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Discussion Starter · #1 ·
hi, i have fuel starvation during acceleration.

happens in every gear and mainly at the top half of the rpm range, no matter how much fuel i add or increase the fuel pressure it still happens.

car holds boost at any boost levels set.

any thoughts to this?

related details on setup:

hks t51r kai bb (recently upgraded from hks to4z)
aem ems
twin denso pumps on oem hanger.
2 x in line fuel filters
hks dli
built engine etc etc etc etc etc etc

thanks

:sadwavey:
 

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Do you have a fuel pressure gauge to check the pressure real time? My buddy's track Evo had the same problem. Turns out the regulator was on its way out and couldn't hold the pressure consistently. Switched out his SARD adjustable FPR to an Aeromotive one and problem fixed.

IME the SARD ones tend to burst their diaphragms over time.
 

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i agree with the above. a fuel pressure gauge is one thing i wish i had mounted in my old car.

i assume you're adjusting the base pressure?

i was having weird problems on my VR4 awhile ago. turns out one of the rubber hoses that connected to one of my in tank pumps had a slit in it and was not allowing the pump to feed half of my cylinders correctly. you could check for freak issues like that.

whatever you do, don't mess around. it's probably what cost me my engine awhile back.
 

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Discussion Starter · #5 ·
hi guys, thanks for the input. i have an update on this...

i changed the Sard Type RJ fuel pressur regulator to the HKS FPR and the problem persists.

and whatever it is it seems to have got worse or is getting worse on test runs.

i have checked the denso pumps and they both work fine, fuel pressure is set to 44psi.

i am using 1 -6 fuel line from the oem banjo and 1 new -6 fuel line from a the hanger. both lines have inline fuel filters and go to each side of the rail.

off boost the car a/f ratio is fine and they way it was mapped originally, on full bost its causing the fuel to lean out.

any help and advise would will greatly appreciated guys.

thanks

:sad:
 

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Sorry to hear your having this problem, doesn't sound fun.

I always run as much fuel in my gas tank as possible to ensure the pumps are not starved.

I'd double check that the fuel from the return feed on the rail is being dumped back into the plastic sub tank inside the actual gas tank. Its possible that you may have left if off when you installed the pumps?

Also check and make sure your pumps are installed as low in the tank as possible, I have seen them so high up that they didnt fit into the plastic sub tank.

When the car is on a dyno does it have the same problem?

Best of luck with the repair.

Adam
 

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Discussion Starter · #7 ·
thanks adam for the quick reply to try and help me resolve this.

i have checked the return line already and it does flow back into the tank like stock and all fittings are proplery secured.

the pumps both sit parallel together at the very bottom of the hanger and my fuel tank is never left low, its always full or half tank at the very lowest point.

i have double and tripple checked the fittings and fictures. i have also tried running single pump at a time to test them out and no problems at all and its also not helped to come to a solution to this problem.

anymore for anymore guys ... :sad:

lee
 

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Ummm check the grounds on ur fuel pumps? Sounds like an electrical issue IMO since its not the regulator?
Good luck trouble shooting!
 

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Discussion Starter · #10 ·
Did you say when you run only one pump at a time, you don't get this problem any longer? It's kind of confusing how it was written. And you have tried each pump by itself?

Alex
no, when i run each pump individually the problem is STILL there, so we know its not the pumps causing the problem and that they are working fine.

thanks

lee
 

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did you get rid for the charcoal can? If you plugged that line, then you need a vented cap or you will have a big vacuum in there and the pumps wont work well.

I have this same problem on my mk3 anytime i go under 1/2 tank i get fuel starvation, and i'm trying to figure it out...
 

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Discussion Starter · #12 ·
did you get rid for the charcoal can? If you plugged that line, then you need a vented cap or you will have a big vacuum in there and the pumps wont work well.

I have this same problem on my mk3 anytime i go under 1/2 tank i get fuel starvation, and i'm trying to figure it out...
you've made me think about something on that note regarding how full the tank is. when the tank is full the lean figures are not so bad (but still not acceptable) as the tank gets lower like to the half way mark it seems to get worse (i think).

yes the charcoal canister is removed and the breather pipe for the fuel tank is NOT blocked off. it still breathes to atmosphere.

keep them coming guys....
 

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Discussion Starter · #13 ·
I have this same problem on my mk3 anytime i go under 1/2 tank i get fuel starvation, and i'm trying to figure it out...
regarding your issue i think i might know what the problem is. if you have jubilee clips holding the fuel hose from the pump to the top (inside of the hanger) and they are not tight enough on one end or either that could lead to fuel "leaking" back into the tank, this would be more apparent when the tank is around half way mark, when its full it shouldnt be that much of a problem. but if the jubilee gets looser then it might get worse even with a full tank.

just my thought bud.
 

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I had the same problem a few months back. As soon as I went into boost around 9lbs I started breaking up and the wide band went lean. It got worse over time. I tried increasing the regulator pressure with no luck. I tried pulling the fuse for each pump and didn't see much drop in pressure. I eventually pulled the pump hanger and while inspecting the pumps I found a cracked line between one of the pumps and the hanger. I replaced it with a new piece. Problem solved.
 

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I know you have already gone through this, but do you have braided lines? or are you running 2 pumps through the stock line? A member on here after installing braided lines was getting a serious lean condition under boost on his single. He checked FP, voltage to the pumps, AEM settings, you name it. His problem was as simple as vhaning his brand new fuel filter. There was a ton of black hose "dust" built up on his filter causing it to restrict fuel flow enough to cause a huge lean spot. He is running Triple densos, -10 fuel rail, aeromotive fpr, -6 return line.

Check the filter if you haven't already.
 
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